how many elements are gaseous at room temperature?

There are a few elements that are gaseous at room temperature, meaning that they are in the gas phase at standard temperature and pressure (STP). STP is defined as a temperature of 20 degrees Celsius (68 degrees Fahrenheit) and a pressure of 101.3 kilopascals (kPa).

The elements that are gaseous at room temperature include:

• Helium (He): Helium is a chemical element with the atomic number 2 and the symbol He. It is a noble gas that is known for its low density and is often used in balloons and airships to provide lift. Helium is also used in a variety of other applications, including welding and MRI machines.

• Neon (Ne): Neon is a chemical element with the atomic number 10 and the symbol Ne. It is a noble gas that is known for its bright orange-red glow when it is electrically excited. Neon is often used in neon lights and other types of lighting applications.

• Argon (Ar): Argon is a chemical element with the atomic number 18 and the symbol Ar. It is a noble gas that is known for its low reactivity and is often used in a variety of industrial and scientific applications, including welding and the production of certain types of glass.

• Krypton (Kr): Krypton is a chemical element with the atomic number 36 and the symbol Kr. It is a noble gas that is known for its low reactivity and is often used in a variety of industrial and scientific applications, including the production of certain types of light bulbs and as a tracer gas in leak detection.

• Xenon (Xe): Xenon is a chemical element with the atomic number 54 and the symbol Xe. It is a noble gas that is known for its low reactivity and is often used in a variety of industrial and scientific applications, including the production of certain types of light bulbs and as a general anesthetic in surgery.

These elements are all gaseous at room temperature because they have a low atomic mass and a low melting point, which allows them to remain in the gas phase at STP. They are also known as the "noble gases" because they are generally unreactive and do not readily form compounds with other elements.